An example of a luminaire in an automobile is the tail light assembly, comprising an outer plastic cover, redirection prisms, a reflector, a socket, and a bulb located at approximately the focal point of the reflector. The bulb may include two filaments, where one filament is energized for a constant tail light, and both filaments are energized for a brighter stop indication. In both cases, the emission pattern of the bulb is lambertian. There may be multiple compartments in the luminaire for side lights and turn signals, and each compartment houses an associated bulb. Since filament bulbs have a lambertian emission, only by changing the optical features of the luminaire can the emission pattern of the luminaire be changed.
Government regulations dictate the emission patterns for all exterior vehicle lighting including, for example, tail lights and head lights. Exterior lighting for vehicles is dominated by standardized filament lamps, which are largely lambertian sources, so the differences in radiation patterns of the luminaires are primarily due to differences in the luminaire design. For different jurisdictions, therefore, a different luminaire must be designed to create the required emission patterns. The result is that the optical features, including color filters, of the luminaire must be different depending on where the vehicle is sold.
Recently, incandescent light bulbs have been substituted with LED bulbs. These solid state bulbs have the same or similar socket connecting features as traditional bulbs, allowing them to be retrofit into existing luminaires. However, the LED bulbs emulate the incandescent bulbs and output a lambertian pattern, where the reflector and other optics in the luminaire are used to shape the beam.
Luminaires, particularly those in cars, often serve more than one purpose. For example, the luminaire needs to provide a color and light pattern to meet regulatory requirements but it is also an important styling element. Recent higher end vehicles have taken much advantage of LEDs and novel optics to create brand-linked styling elements, such as BMW's light rings for a front position lamp, or Audi's “eyebrow light” for a daytime running lamp. Also, in the rear of the car, the tail lamp has become an important styling element, with each car model show-casing a new look but maintaining features that link to the car brand.
As with all fashion elements, the “refresh time” is important to keeping the luminaire, and therefore the vehicle, looking fresh and modern. Refresh times for vehicles have reduced over many decades of car production and, as of this writing, are typically 2-3 years for a car model refresh and 4-5 years for completely new car models. New vehicle luminaires have similar 2-3 year design and manufacturing cycles and are often some of the most visible styling features of a car. Luminaires like the stop/tail rear lamp are designed to fit a single bulb type, and different luminaires are designed to meet the regulated radiation pattern and styling needs of different countries and/or regulated regions. One result is that a single car model can therefore require several different luminaires to be designed and manufactured to meet different regulations and, when styling refresh is desired, the luminaire must again be redesigned and separately manufactured.
WO2011/131197A1 discloses an illumination device with an assembly of at least two groups of light sources, which light sources are individually controllable. Each group of light sources is assembled with different lenses, mixers or reflectors. The first group of light sources is configured to pass through non-diffusing regions of a diffuser cover, and the second group of light sources is configured to pass through diffusing regions of the diffuser cover.
What is needed is a luminaire whose light emission can be rapidly and inexpensively changed to meet different regulated requirements and to have different styling features.